In the year 2112 the Pacific hot-spot (that formed Hawaii) unexpectedly erupted cataclysmically; resulting in the world's largest caldera and most notable landmark - a gigantic rock-ring in the middle of the ocean. Almost a century later the location still displays majestic geological activity and electromagnetic phenomena.

I'd say this is one of your better pieces. I like the use of the minimal colors here. If I were you though, I'd drop the little river on the big one, and add more texture to the rocks in the background. Other than that, this piece is very neat. So keep at it!